Remotely controllable modular power control device for power generation

ABSTRACT

A power adjusting circuit includes a sensor configured to measure a voltage and a current of the first AC output by an inverter, an AC/DC/AC converter configured to receive the first AC output from the inverter, and a controller configured to convert the first AC output to a second AC output having a desired power factor.

BACKGROUND

The present invention relates to the field of power generation, and moreparticularly to the use of distributed power generation systems tosupply both real and reactive power to an electrical grid.

An electrical grid is an interconnected network for deliveringelectricity from suppliers to consumers. It usually consists ofgenerating stations that produce electrical power, high-voltagetransmission lines that carry power from distant sources to demandcenters, and distribution lines that connect individual customers. Thepower provided by the grid typically includes a combination of activepower (real power), measured in watts, and reactive power measured involt-amperes reactive (“var”).

An electrical grid may contain many distributed generation sources. Forexample, a resident can supplement the power from the grid (“gridpower”) that is provided to their residence with power generated by aresidential power generation system (“local power”) installed within theresidence. For example, the residential power generation system couldprovide 10% of the power required to the residence while the gridprovides the remaining 90%. When the power generated by the residentialpower generation system is greater than the needs of the residence, theresidential power generation system can supply power to the grid so itcan be used by other residences.

A photovoltaic (PV) system is an example of a residential powergeneration system. A PV system converts sunlight directly toelectricity. A PV system works any time the sun is shining, but moreelectricity is produced when the sunlight is more intense. A typical PVsystem provides only active power and is incapable of providing reactivepower.

SUMMARY

According to an exemplary embodiment of the inventive concept, a poweradjusting circuit includes a sensor configured to measure a voltage anda current of the first AC output by an inverter, an AC/DC/AC converterconfigured to receive the first AC output from the inverter, and acontroller configured to convert the first AC output to a second ACoutput having a desired power factor.

According to an exemplary embodiment of the inventive concept, a poweradjusting circuit includes a sensor configured to measure a voltage anda current of a first AC output by an inverter, a first AC/DC/ACconverter configured to receive the first AC output from the inverterand a first controller configured to control the first AC/DC/ACconverter, and a second AC/DC/AC converter configured to receive thefirst AC output from the inverter and a second controller configured tocontrol the second AC/DC/AC converter. The controllers negotiate withone another to determine first and second amounts of power to provide.The first controller applies a first adjustment signal to the firstAC/DC/AC converter based on the first amount and the second controllerapplies a second adjustment signal to the second AC/DC/AC converterbased on the second amount, to cause the AC/DC/AC converters tocollectively generate a second AC output which is different from thefirst AC output.

According to an exemplary embodiment of the inventive concept, a poweradjusting circuit includes a sensor configured to measure a voltage anda current of a first AC output by an inverter, a first AC/DC/ACconverter configured to receive the first AC output from the inverterand a first controller configured to control the first AC/DC/ACconverter, a second AC/DC/AC converter configured to receive the firstAC output from the inverter and a second controller configured tocontrol the second AC/DC/AC converter, and a central controllerconfigured to inform the first controller of a first amount of power toprovide and inform the second controller of a second amount of power toprovide. The first controller applies a first adjustment signal to thefirst AC/DC/AC converter based on the first amount and the secondcontroller applies a second adjustment signal to the second AC/DCconverter based on the second amount, to cause the AC/DC/AC convertersto collectively generate a second AC output which is different from thefirst AC output.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Through the more detailed description of some embodiments of the presentdisclosure in the accompanying drawings, features of the presentdisclosure will become more apparent, wherein:

FIG. 1 illustrates a cloud computing environment according to anembodiment of the present invention;

FIG. 2 depicts abstraction model layers according to an embodiment ofthe present invention, which may be used to implement a power managementcontroller;

FIG. 3 shows an exemplary computer system, in which the power managementcontroller may reside;

FIG. 4 shows a system according to an exemplary embodiment of theinvention that includes the power management controller;

FIG. 5 shows a system according to an exemplary embodiment of theinvention that includes the power management controller.

FIG. 6 illustrates a method of supplying power according to an exemplaryembodiment of the inventive concept;

FIG. 7 illustrates a method of communicating power-set points accordingto an exemplary embodiment of the inventive concept;

FIG. 8 illustrates a method of communicating power-set points accordingto an exemplary embodiment of the inventive concept;

FIG. 9A and FIG. 9B show examples of in-phase voltage and currents andout-of phase voltage and currents, respectively; and

FIG. 10 illustrates an embodiment of an AC/DC/AC converter of thesystems of FIG. 4 and FIG. 5.

DETAILED DESCRIPTION

The inventive concept will be described in more detail with reference tothe accompanying drawings, where exemplary embodiments of the presentdisclosure have been illustrated. Throughout the drawings, same or likereference numerals are used to represent the same or like components.However, the present inventive concept can be implemented in variousmanners, and thus should not be construed to be limited to theembodiments disclosed herein. On the contrary, those embodiments areprovided for the thorough and complete understanding of the presentdisclosure to convey the scope of the present disclosure to thoseskilled in the art.

It is understood in advance that although this disclosure includes adetailed description on cloud computing, implementation of the teachingsrecited herein are not limited to a cloud computing environment. Rather,embodiments of the present invention are capable of being implemented inconjunction with any other type of computing environment now known orlater developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a shared pool of configurable computingresources (e.g. networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider. Broad network access: capabilities are availableover a network and accessed through standard mechanisms that promote useby heterogeneous thin or thick client platforms (e.g., mobile phones,laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter).

Rapid elasticity: capabilities can be rapidly and elasticallyprovisioned, in some cases automatically, to quickly scale out andrapidly released to quickly scale in. To the consumer, the capabilitiesavailable for provisioning often appear to be unlimited and can bepurchased in any quantity at any time.

Measured service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported providing transparency for both theprovider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based e-mail).The consumer does not manage or control the underlying cloudinfrastructure including network, servers, operating systems, storage,or even individual application capabilities, with the possible exceptionof limited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as follows:

Private cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting forload-balancing between clouds). A cloud computing environment is serviceoriented with a focus on statelessness, low coupling, modularity, andsemantic interoperability. At the heart of cloud computing is aninfrastructure comprising a network of interconnected nodes. Referringnow to FIG. 1, illustrative cloud computing environment 50 is depicted.As shown, cloud computing environment 50 comprises one or more cloudcomputing nodes 10 with which local computing devices used by cloudconsumers, such as, for example, personal digital assistant (PDA) orcellular telephone 54A, desktop computer 54B, laptop computer 54C,and/or automobile computer system 54N may communicate. Nodes 10 maycommunicate with one another. They may be grouped (not shown) physicallyor virtually, in one or more networks, such as Private, Community,Public, or Hybrid clouds as described hereinabove, or a combinationthereof. This allows cloud computing environment 50 to offerinfrastructure, platforms and/or software as services for which a cloudconsumer does not need to maintain resources on a local computingdevice. It is understood that the types of computing devices 54A-N shownin FIG. 1 are intended to be illustrative only and that computing nodes10 and cloud computing environment 50 can communicate with any type ofcomputerized device over any type of network and/or network addressableconnection (e.g., using a web browser).

Referring now to FIG. 2, a set of functional abstraction layers providedby cloud computing environment 50 (FIG. 1) is shown. It should beunderstood in advance that the components, layers, and functions shownin FIG. 2 are intended to be illustrative only and embodiments of theinvention are not limited thereto. As depicted, the following layers andcorresponding functions are provided:

Hardware and software layer 60 includes hardware and softwarecomponents. Examples of hardware components include: mainframes 61; RISC(Reduced Instruction Set Computer) architecture based servers 62;servers 63; blade servers 64; storage devices 65; and networks andnetworking components 66. In some embodiments, software componentsinclude network application server software 67 and database software 68.

Virtualization layer 70 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers71; virtual storage 72; virtual networks 73, including virtual privatenetworks; virtual applications and operating systems 74; and virtualclients 75.

In one example, management layer 80 may provide the functions describedbelow. Resource provisioning 81 provides dynamic procurement ofcomputing resources and other resources that are utilized to performtasks within the cloud computing environment. Metering and Pricing 82provide cost tracking as resources are utilized within the cloudcomputing environment, and billing or invoicing for consumption of theseresources. In one example, these resources may comprise applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal 83 provides access to the cloud computing environment forconsumers and system administrators. Service level management 84provides cloud computing resource allocation and management such thatrequired service levels are met. Service Level Agreement (SLA) planningand fulfillment 85 provide pre-arrangement for, and procurement of,cloud computing resources for which a future requirement is anticipatedin accordance with an SLA.

Workloads layer 90 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation 91; software development and lifecycle management 92; virtualclassroom education delivery 93; data analytics processing 94;transaction processing 95; and a power management controller 96. Thepower management controller 96 is used to control a local poweradjusting circuit that interfaces with a residential power generationsystem, and will be discussed in more detail below.

FIG. 3 illustrates an embodiment of a computer server that may be usedto implement part of computing devices 54A-54N, the power managementcontroller 96, or the global controller 490, which is applicable toimplementing embodiments of the present invention. Computersystem/server 12 is only illustrative and is not intended to suggest anylimitation as to the scope of use or functionality of embodiments of theinvention described herein.

As shown in FIG. 3, the computer system/server 12 is shown in the formof a general-purpose computing device. The components of the computersystem/server 12 may include, but are not limited to, one or moreprocessors or processing units 16, a system memory 28, and a bus 18 thatcouples various system components including system memory 28 toprocessor 16.

Bus 18 represents one or more of any of several types of bus structures,including a memory bus or memory controller, a peripheral bus, anaccelerated graphics port, and a processor or local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include an Industry Standard Architecture (ISA) bus,a Micro Channel Architecture (MCA) bus, an Enhanced ISA (EISA) bus, aVideo Electronics Standards Association (VESA) local bus, and aPeripheral Component Interconnect (PCI) bus.

The computer system/server 12 may include a variety of computer systemreadable media. Such media may be any available media that is accessibleby the computer system/server 12, and it includes both volatile andnon-volatile media, removable and non-removable media.

The system memory 28 can include computer system readable media in theform of volatile memory, such as random access memory (RAM) 30 and/orcache memory 32. The computer system/server 12 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example, storage system 34 can be provided for readingfrom and writing to a non-removable, non-volatile magnetic media (notshown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 18 by one or more datamedia interfaces. As will be further depicted and described below,memory 28 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

A program/utility 40, having a set (at least one) of program modules 42,may be stored in memory 28 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. The program modules 42 generally carry out the functionsand/or methodologies of embodiments of the invention as describedherein.

The computer system/server 12 may also communicate with one or moreexternal devices 14 such as a keyboard, a pointing device, a display 24,etc.; one or more devices that enable a user to interact with thecomputer system/server 12; and/or any devices (e.g., network card,modem, etc.) that enable the computer system/server 12 to communicatewith one or more other computing devices. Such communication can occurvia Input/Output (I/O) interfaces 22. The computer system/server 12 cancommunicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via a network adapter 20. As depicted, the network adapter20 communicates with the other components of computer system/server 12via the bus 18. It should be understood that although not shown, otherhardware and/or software components could be used in conjunction withthe computer system/server 12. Examples of these other hardware and/orsoftware components include, but are not limited to: microcode, devicedrivers, redundant processing units, external disk drive arrays, RAIDsystems, tape drives, and data archival storage systems.

FIG. 4 shows a system according to an exemplary embodiment of theinvention. The system includes the power management controller 96 ofFIG. 2, a photovoltaic (PV) array 410, a PV inverter system 420, acurrent and voltage sensor 450, and a local power adjusting circuit 460.The PV inverter 420 includes a DC/DC converter 423 and a DC/AC converter426. The DC/DC converter 423 is designed to convert a first DC signalinput to the DC/DC converter 423 to a different second DC signal. TheDC/AC converter 426 is designed to convert the second DC signal to an ACsignal that is compatible with the main power Grid 440. For example, inNorth America, the AC signal is typically 120 v with a frequency of 60Hz, and in Europe, the AC signal is typically 230 v with a frequency of50 Hz. FIG. 4 also depicts a local AC load 430 that corresponds to theload of a device (e.g., a light, appliance, etc.) consuming power of theAC signal.

When the PV inverter system 420 provides a first AC output includingonly active power (e.g., no reactive power), the local adjusting circuit460 is capable of performing an operation on the first AC output togenerate a second AC output including both active power and reactivepower or only reactive power, and provide the second AC output to theGrid 440.

The local adjusting circuit 460 may receive a request signal from anexternal source such as the power management controller 96 across acomputer network, the Internet, or across one or more of the cloudcomputing nodes 10. The power management controller 96 may communicatethe request message to the local adjusting circuit 460 using the networkadaptor 20. The power management controller 96 or the network adaptor 20may include a transceiver to wirelessly transmit the request signal tothe central controller 490. The central controller 490 may include thenetwork adaptor 20 to receive the request signal or a transceiver towirelessly receive the request signal.

In an embodiment, the request signal includes a requested amount ofreactive power (e.g., a certain amount of reactive current) and arequested amount of active power (e.g., a certain amount of activecurrent). For example, the request signal could include a request forpartial reactive power and partial active power. In an embodiment, therequest signal includes requests for particular harmonics (e.g., adistortion of the current that introduces harmonics). For example, therequest signal could include a request for additional power in the5^(th) harmonic. In an embodiment, the request signal includes arequested amount of reactive power, a requested amount of active power,and a requested amount of harmonics.

The local adjusting circuit 460 includes the central controller 490, aplurality of AC/DC/AC converters 471, 472, . . . , 47 n, and a pluralityof local controllers 481, 482, . . . , 48 n. In an embodiment, eachlocal controller is a digital signal processing system, which isoptically isolated and can drive switches of the AC/DC/DC convertersusing a pulse width modulation signal. While the local adjusting circuit460 is depicted as including several AC/DC/AC converters and severallocal controllers, in an alternate embodiment, only a single AC/DC/ACconverter and a single local controller are present. Further, in thisembodiment, the single local controller performs the functions of thecentral controller 490 and the central controller 490 is omitted. Themultiple AC/DC/AC converters and local controllers allow the localadjusting circuit 460 to operate in a modular fashion. Each AC/DC/ACconverter and local controller pair can be controlled by the centralcontroller 490 to handle the reactive/active power requirements as wellas a portion of the harmonic requirements. For example, the first localcontroller 481 could be controlled to handle part of the reactive powerrequirements and the second controller 482 could be controlled to handlepart of the reactive power requirements. For example, the first localcontroller 481 could be controlled to introduce 5^(th) harmonics whilethe second controller 482 could be controlled to introduce 7^(th)harmonics.

In an embodiment, the voltage and current sensor 450 is a non-contactcurrent and voltage sensor such as a Hall effect sensor. The sensor mayinclude a housing that contains the current and voltage sensors, whichmay be a ferrite cylinder, loop, or ring with a Hall effect sensordisposed in a gap along the circumference to measure current, or in thealternative, a winding provided through the cylinder along its axis anda capacitive plate or wire disposed adjacent to, or within, the ferritecylinder to provide an indication of the voltage. For example, thecylinder, loop, or ring may encircle the wire connected to an outputterminal of the PV inverter 420.

The central controller 490 can operate on a measured current and voltagereceived from the voltage and current sensor 450 to determine the amountof active power and reactive power presently being generated. Forexample, it is initially assumed that the measured current and measuredvoltage are in phase with one another like in FIG. 9A, and thus onlyactive power is being provided. For example, if the measured current is5 amps and the measured voltage is 110 volts, 550 watts of active poweris available with 0 var of reactive power. Assuming the power managementcontroller 96 has requested 550 vars of reactive power, it would befeasible that the requested amount of power (i.e., 0% active power and100% reactive power) can be provided. However, since no reactive poweris presently available, the central controller 490 needs to providesignals to one or more of the local controllers 481, 482, . . . , 48 nalong local bus 492 to inform the respective local controllers of theamount of reactive power each is to support. The central controller 490can make this decision based on the individual efficiencies and powercapacities of the respective AC/DC/AC converters.

In a first example, only the first local controller 481 is used. In thisexample, the central controller 490 provides a signal to the first localcontroller 481 indicating that it is to provide only reactive power.Since no reactive power is currently being provided, the first localcontroller 481 applies a signal to the first AC/DC/AC converter 471 thatcauses the first AC/DC/AC converter to operate on the first AC outputfrom the PV inverter system 420 to generate a second AC output thatprovides entirely reactive power. For example, if the current andvoltage of the first AC signal are entirely in phase with one another,the first local controller 481 applies an adjustment signal to the firstAC/DC/AC converter 471 that causes the first AC/DC/AC converter 471 togenerate the second AC output such that the phase of current of thesecond AC output is out of phase by 90 degrees with the voltage of thesecond AC output.

In an embodiment, each local controller includes a phase locked loop(PLL) that measures a voltage, frequency, and phase of the grid 440. Forexample, FIG. 4 and FIG. 5 show a connection from the first localcontroller 481 to the grid 440. Once the PLL locks onto the informationof the grid 440, real/active power and reactive power can be provided.Supplying current in-phase with a voltage of the grid 440 corresponds toreal power at a power factor of 1 and supplying power out-of-phase withthe voltage of the grid 440 corresponds to real and reactive power witha power factor not equal to 1. The figures only show the grid 440 beingconnected to one of the local controllers for ease of illustration.However, the other local controllers may be additionally connected tothe grid 440 to enable their respective PLL to perform the abovemeasuring and locking.

For example, if the central controller 490 provides power requirementsto the first local controller 481, the first controller 481 computes atarget current with an associated target voltage, and the first localcontroller 481 changes the voltage output of the first AC/DC/ACconverter 471 to meet the target voltage in such a way that an outputcurrent of the first AC/DC/AC converter 471 reaches the target current.For example, the first local controller 481 may apply a PWM signal(e.g., an adjustment signal) to internal switches of the first AC/DC/ACconverter 471 to meet the target voltage.

In an exemplary embodiment, the first local controller 481 periodicallyapplies the adjustment signal to the first AC/DC/AC converter 471 tomake small adjustments in the phase difference among the measuredcurrent and voltage until it reaches the desired phase difference. Forexample, if a 90 degree phase difference is desired, the first localcontroller 481 could apply an adjusting signal to the first AC/DC/ACconverter 471 periodically (e.g., every millisecond) thatincreases/decreases the phase difference by a small amount (e.g., 2degrees) until the desired phase difference (e.g., 90 degrees) isachieved.

In another example, it is assumed that two of local controllers 481 and482 and their corresponding AC/DC/AC converters 471 and 472 are used,and the central controller 490 has informed the first local controller481 it is to provide a power factor of 0 (all reactive power) andinformed the second local controller 481 it is to provide a power factorof 0.707 (some reactive and some real power). For example, if the secondAC/DC/AC converter 472 is outputting 5 amps and 110 volts, when set to apower factor of 0.707, it would output about 389 watts of Active power(e.g., cosine of 45 degree phase angle (i.e., a power factor of 0.707)*5amps*110 volts), and 389 vars of Reactive power (e.g., sine of 45degrees*5 amp*110 volts). For example, the first local controller 481may apply a first adjustment signal to the first AC/DC/AC converter 471to set the first AC/DC/AC converter 471 to a power factor of 0 and thesecond local controller 482 may apply a second adjustment signal to thesecond AC/DC/AC converter 472 to set the second AC/DC/AC converter tothe power factor of 0.707.

While the above examples reference phase differences of 0 degrees and 45degrees, and power factors of 0 and 0.707, the invention is not limitedthereto. For example, various phase differences and power factors may beused to achieve various amounts of reactive and active power.

In addition, different local controllers may supply different harmonics.In an embodiment, each local controller may be uniquely designed toadditionally introduce one requested harmonic at the required level ofpower. In another embodiment, each local controller may supply apartially or fully distorted current such that the sum of all localcontrollers' outputs results in a waveform having the harmonics asrequested.

FIG. 5 illustrates a variation on the embodiment depicted in FIG. 4. InFIG. 5, the central controller 490 is omitted. The local controllers 481receive the voltage and current measurements from the sensor 450 andreceive the requests from the power management controller 96 for variouscombinations of active, reactive, and/or harmonic power. The localcontrollers 481-48 n can determine how much power is presently beingprovided by the PV system 120 from the sensed voltage and current, thetypes of power (e.g., reactive, active, harmonic) and the amounts ofthese types or the current power factor. The local controllers 481-48 ncommunicate with one another through bus 493 to decide amongstthemselves how much of the various types of power they will beresponsible for providing. For example, if the first local controller481 determines from the capacity and efficiency of the first AC/DC/ACconverter 471, that it can provide 80% of the reactive and active powerrequirements and the second controller 482 determines from the capacityand efficiency of the second AC/DC/AC converter 472, that it can provide40% of the reactive and active power requirements, they could negotiatewith one another such that the first controller 481 ultimately isresponsible for 70% while the second controller is ultimatelyresponsible for 30%.

FIG. 6 illustrates a method of supplying power that can be applied toeither the system of FIG. 4 or the system of FIG. 5. The method includesoutputting the current and voltage measurements (S601). For example, ifthe system of FIG. 4 is used, then the current and voltage measurementsare output to the central controller. For example, if the system of FIG.5 is used, then the current and voltage measurements are output to thelocal controllers 481-48 n. The method then includes determining whethera central controller is present (S602). This determination can beperformed by the local controllers 481-4 n. For example, if the localcontrollers 481-48 n ping the central controller 490, and receive noresponse, it can be concluded that no central controller is available.If the central controller is present, then the system of FIG. 4 is thesystem being used. The local controllers 481-48 n then receive the powerset-points from the central controller (S603). For example, upondetermining that the central controller 490 is available, the localcontrollers 481-48 n can send messages to the central controller 490requesting information on the amounts of power and types of powerneeded. The power set-points may correspond to the amounts of power andthe types of power needed. If the central controller 490 is notavailable (e.g., system of FIG. 5), the local controllers 481-48 ncompute the power set-points (e.g., power factors) themselves based oncommunications between themselves (S604). Once the power set-points havebeen computed or received, the local controllers supply the requiredpower based on the power set points (S605).

FIG. 7 is a method that can be applied to the system of FIG. 4. Thecentral controller 490 receives commands from an outside source (S701).For example, the central controller 490 may receive a command from thepower management controller 96 that indicates a certain amount of powerto provide and the breakdown of the different types (e.g., reactive,active, harmonic) and the amounts of each to provide. The methodincludes computing the power set-points for the local controllers basedon one or more local factors (S702). For example, the computation cam beperformed by the central controller 490 taking into consideration powerefficiencies and power capacities of the AC/DC/AC converters 471-47 n.For example, each set-point may correspond to one of a selected group ofthe local controllers, where each set point indicates amounts and typesof power to provide. The method includes communicating the computedpower set-points to the local controllers (S703). For example, thecentral controller 490 may send the power set-points to the respectivelocal controllers using bus 492 in FIG. 4.

FIG. 7 is a method that can be applied to the system of FIG. 5. Themethod includes a selected one or more of the local controllersreceiving commands from an outside source (S801). For example, theoutside source may be the power management controller 96 and thecommands may request a certain amount of active, real, and/or harmonicpower (i.e., the power requirements). The method includes the selectedcontrollers communicating with one another (S802) and reaching aconsensus on the power set-points (S803). For example, the localcontrollers of FIG. 5 can negotiate with one another based on thecurrent amounts and types of power being provided by the PV system 420,the power requirements, to reach a consensus that indicates how muchpower of the power requirements they are responsible for providing.

FIG. 10 illustrates an embodiment of an AC/DC/AC converter of FIG. 4 orFIG. 5. For example, the AC/DC/AC converter 471 may include an AC/DCconverter, a DC link capacitor, a DC/AC converter connected in parallelwith one another. The AC/DC converter receives a first AC signal outputfrom the PV inverter 420 and provides a DC output to the DC linkcapacitor to charge the DC link capacitor. The DC link capacitorprovided input to the DC/AC converter, which converts the DC output to asecond AC signal. Even when the first AC signal only includes activepower, the second AC signal may include both active power and reactivepower, as well as additional harmonics.

The present invention may be a system, and parts of the preventinvention may be implemented by a method, and/or a computer programproduct. The computer program product may include a computer readablestorage medium (or media) having computer readable program instructionsthereon for causing a processor to carry out aspects of the presentinvention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A power adjusting circuit comprising: a sensorpositioned at an output of an inverter to measure a voltage and acurrent of a first AC signal output by the inverter; an AC/DC/ACconverter connected to the output of the inverter to receive the firstAC signal output from the inverter; and a controller wirelessly receivesa request signal including a first amount of desired active power and asecond amount of desired reactive power, determines a third amount ofactive power and a fourth amount of reactive power in the first ACsignal from the measured voltage and current, determines an adjustmentsignal based on the first through fourth amounts, and applies theadjustment signal to the AC/DC/AC converter to cause the AC/DC/ACconverter to convert the first AC signal to a second AC signal havingthe first amount of the desired active power and the second amount ofthe desired reactive power, wherein the inverter comprises a DC/DCconverter receiving an output of a photovoltaic array and a DC/ACconverter receiving an output of the DC/DC converter.
 2. The poweradjusting circuit of claim 1, wherein the first AC signal is at a unitypower factor and the second AC signal is at a desired power factor notequal to the unity power factor.
 3. The power adjusting circuit of claim1, wherein the controller determines a fifth amount of harmonic power inthe first AC signal, the request signal includes a sixth amount ofdesired harmonic power, the controller determines the adjustment signalby further using the fifth and sixth amounts, and the adjustment signalfurther causes the second AC signal to include the sixth amount of thedesired harmonic power.
 4. The power adjusting circuit of claim 2,wherein the controller applies the adjustment signal to the AC/DC/ACconverter periodically to gradually convert the first AC signal havingthe unity power factor to the second AC signal having the desired powerfactor.
 5. The power adjusting circuit of claim 1, wherein the AC/DC/ACconverter comprises an AC/DC converter, a DC link capacitor, and a DC/ACconverter connected in parallel with one another, wherein the AC/DCconverter receives the first AC signal output by the inverter.
 6. Thepower adjusting circuit of claim 1, wherein the sensor is a Hall effectsensor including a portion encircling a wire connected to an output ofthe inverter.
 7. A power adjusting circuit comprising: a sensorpositioned at an output of an inverter to measure a voltage and acurrent of a first AC signal output by the inverter; a first AC/DC/ACconverter connected to the output of the inverter to receive the firstAC signal output from the inverter and a first controller that controlsthe first AC/DC/AC converter; and a second AC/DC/AC converter connectedto the output of the inverter to receive the first AC signal output fromthe inverter and a second controller that controls the second AC/DC/ACconverter, wherein the controllers negotiate with one another todetermine first and second amounts of active power to provide, and thirdand fourth amounts of reactive power to provide, wherein the firstcontroller applies a first adjustment signal to the first AC/DC/ACconverter based on the first amount and the third amount and the secondcontroller applies a second adjustment signal to the second AC/DC/ACconverter based on the second amount and fourth amount, to cause theAC/DC/AC converters to collectively generate a second AC signal having adifferent power factor from the first AC signal, the second AC signalhaving an amount of active power totaling the first and second amountsand an amount of reactive power totaling the third and fourth amounts.8. The power adjusting circuit of claim 7, wherein the first AC signalhas current in phase with a grid voltage and the second AC signal hascurrent that is in or out of phase with the grid voltage.
 9. The poweradjusting circuit of claim 7, wherein the first AC signal consistsentirely of active power and the second AC signal contains reactive andharmonic power.
 10. The power adjusting circuit of claim 7, wherein thecontrollers wirelessly receive a total of the first and second amountsof active power and a total of the third and fourth amounts of reactivepower to generate.
 11. The power adjusting circuit of claim 7, whereineach AC/DC/AC converter comprises an AC/DC converter, a DC linkcapacitor, and a DC/AC converter connected in parallel with one another,wherein the AC/DC converter receives the first AC signal output by theinverter.
 12. The power adjusting circuit of claim 7, wherein theinverter comprises a DC/DC converter receiving an output of aphotovoltaic array and a DC/AC converter receiving an output of theDC/DC converter.
 13. The power adjusting circuit of claim 7, wherein thesensor is a Hall effect sensor including a portion encircling a wireconnected to an output of the inverter.
 14. The power adjusting circuitof claim 7, wherein the controllers apply their respective adjustmentsignals to their respective AC/DC/AC converters periodically togradually produce the second AC signal having the power factor.
 15. Apower adjusting circuit comprising: a sensor positioned at an output ofan inverter to measure a voltage and a current of a first AC signaloutput by the inverter; a first AC/DC/AC converter connected to anoutput of the inverter to receive the first AC signal output from theinverter and a first controller that controls the first AC/DC/ACconverter; a second AC/DC/AC converter connected to an output of theinverter to receive the first AC signal output from the inverter and asecond controller that controls the second AC/DC/AC converter; and acentral controller informs the first controller of a first amount ofpower to provide and informs the second controller of a second amount ofpower to provide, wherein the first controller applies a firstadjustment signal to the first AC/DC/AC converter based on the firstamount and the second controller applies a second adjustment signal tothe second AC/DC converter based on the second amount, to cause theAC/DC/AC converters to collectively generate a second AC signal having adesired power factor different from the first AC signal, wherein,periodically, the first controller applies the first adjustment signalto the first AC/DC/AC converter and the second controller applies thesecond adjustment signal to the second AC/DC/AC converter, to graduallyproduce the second AC signal having the desired power factor.
 16. Thepower adjusting circuit of claim 15, wherein the first AC output hascurrent in phase with grid voltage and the second AC output has currentthat is in or out of phase with the grid voltage.
 17. The poweradjusting circuit of claim 15, wherein the first AC output consistsentirely of active power and the second AC output contains at least oneof reactive and harmonic power.
 18. The power adjusting circuit of claim15, wherein each controller is configured to wirelessly receive anamount of active power and an amount of reactive power to generate. 19.The power adjusting circuit of claim 15, wherein each AC/DC/AC convertercomprises an AC/DC converter, a DC link capacitor, and a DC/AC converterconnected in parallel with one another, wherein the AC/DC converterreceives an AC output of the inverter.
 20. The power adjusting circuitof claim 15, wherein the inverter comprises a DC/DC converter receivingan output of a photovoltaic array and a DC/AC converter receiving anoutput of the DC/DC converter.
 21. The power adjusting circuit of claim15, wherein the sensor is a Hall effect sensor including a portionencircling a wire connected to an output of the inverter.
 22. The poweradjusting circuit of claim 10, wherein the controllers negotiate withone another to determine fifth and sixth amounts of harmonic power toprovide, wherein the first controller applies the first adjustmentsignal to the first AC/DC/AC converter based further on the fifth amountof harmonic power, and wherein the second controller applies the secondadjustment signal to the second AC/DC/AC converter based further on thesixth amount of harmonic power.